Belg. J. Zool., 134 (2/1) : 29-35 July 2004

Comparative study of courtship and copulation in five Oedothorax species

Liesbeth Maes1, Danny Vanacker1, Sylvia Pardo1 and Jean-Pierre Maelfait 1,2

1 Research Group of Terrestrial Ecology, Ghent University, Ledeganckstraat 35, 9000 Gent, Belgium 2 Institute of Nature Conservation, Kliniekstraat 25, 1070 Brussels, Belgium Corresponding author : L. Maes, e-mail :[email protected] (or [email protected])

ABSTRACT. Oedothorax gibbosus (Blackwall, 1841) is a dwarf restricted to oligo- and mesotrophic alder carrs. This dwarf spider is distinguished from other Oedothorax species by its male dimorphism; gibbosus males are characterised by a hunch and a hairy groove on their carapace, tuberosus males do not have these features. The hairy groove is important during gustatorial courtship behaviour; this is the uptake of secretions by the female from a male body part during courtship. Another remarkable difference between O. gibbosus and its sister species is that courtship and copulation duration is much longer in this species. The rare O. gibbosus also seem to be less active than common spiders of O. fuscus (Blackwall, 1834), O. retusus (Westring, 1851) and O. apicatus (Black- wall, 1850). In that way common spiders raise their chances of survival in the open field. A more active lifestyle seems to be related to a shorter, heavier courtship and copulation. It is also possible that the longer courtship and copulation time, useful for male competition and sperm competition, results from the male dimorphism in this spe- cies. The web has an important function in the reproduction of Oedothorax spiders : it is necessary during gustato- rial courtship, other courtship activities and copulation, and it is also probably important for the distribution of con- tact pheromones. The copulation of Oedothorax species differs from that of : instead of two continuous insertions, we observed, in this case, a series of very short insertions, which can be linked to one other to make up longer periods.

KEY WORDS : Araneae, , Oedothorax, Erigone, gustatorial courtship, courtship, copulation, comparative study.

INTRODUCTION However, the cephalic part of an O. agrestis male is very similar to that of the tuberosus morph of O. gibbosus; the The dwarf spider O. gibbosus (Blackwall, 1841) is a posterior part of the carapace of tuberosus is slightly rather rare spider in Flanders. It can be found in wet to higher than that of O. agrestis males. In O. retusus, the very wet habitats, such as oligo- and mesotrophic alder anterior part of the carapace is strongly raised and there is carrs (DE KEER & MAELFAIT, 1989; ALDERWEIRELDT, only one hair on the clypeus (ALDERWEIRELDT, 1992). On 1992). Besides O. gibbosus, other representatives of the both sides of the carapace, there are grooves with pores genus Oedothorax are present in Belgium : O. apicatus (SCHAIBLE et al., 1986). O. apicatus also possesses lateral (Blackwall, 1850), O. agrestis (Blackwall, 1853), O. fus- grooves (SCHAIBLE et al., 1986) and only one hair on the cus (Blackwall, 1834) and O. retusus (Westring, 1851). O. clypeus (ALDERWEIRELDT, 1992). Typical for this species agrestis is even more rare than O. gibbosus, and is also is the presence of a narrow protuberance on the highest restricted to wet to very wet habitats (DE KEER & MAEL- part of the male carapace (SCHAIBLE et al., 1986; ROB- FAIT, 1989). The other three species on the other hand are ERTS, 1987). among the most common spider species in Belgium. They Dwarf spiders of the genus Oedothorax are approxi- frequently occur in enormous numbers in various types of mately 3 mm long and the females are bigger than the habitats (ALDERWEIRELDT, 1992). males. Most of the time, copulation takes place upside Only one representative of the genus Oedothorax, O. down in the web. In this way, the male finds itself above the gibbosus, is characterised by male dimorphism (DE KEER female and inserts a palp in the epigyne. Each time a small & MAELFAIT, 1989). The genetically dominant (MAELFAIT quantity of sperm is transmitted from the palp into the et al., 1990; VANACKER et al., 2001b) gibbosus morph female spermathecae, by means of a hydraulic pumping possesses a large protuberance on the last third of the car- system of the haematodoch-bladder (FOELIX, 1996). In apace, preceded by a hairy groove. The tuberosus morph many cases, copulation is preceded by courtship, which on the other hand does not possess such a groove and its can have a gustatorial character and can be considered as carapace is smooth and convex. ‘nuptial feeding’. The term ‘nuptial feeding’ refers to any In O. fuscus the highest point of the male carapace is form of offering food by the male to the female, during or situated in the anterior part, and there is typically a pale immediately after the courtship or (and) copulation region in the middle of the abdomen of the female. On the (VAHED, 1998). The phenomenon of secretion in cephalot- clypeus there are two long hairs (ALDERWEIRELDT, 1992). horacic protrusions is not an exclusive character of the This last feature is also typical for O. agrestis males. family . Such secretions are also found in other 30 Liesbeth Maes, Danny Vanacker, Sylvia Pardo and Jean-Pierre Maelfait

families, for example in Argyrodes antipodiana O.P.-Cam- ture about the courtship and copulation behaviour of other bridge, 1880 (Theridiidae) (WHITHOUSE, 1987). spider species is reviewed as well. VANACKER et al. (in press) mentioned several interspe- cific gustatorial courtships by a gibbosus male, and a MATERIALS AND METHODS male or female of the closely related species O. fuscus. These interspecific interactions suggest that the hairy The dwarf spiders were captured manually. O. gibbosus groove in the gibbosus male morph is a nuptial feeding spiders were caught in the nature reserve Het Walenbos at device possibly under the influence of sexual selection. Tielt-Winge, 30-km northeast of Brussels. Representatives The interspecific interactions can possibly be interpreted of O. fuscus and O. retusus came from the military domain as ‘robbings’ of the nuptial feeding (VANACKER et al., in de Yzermonding at Lombardsijde. O. apicatus spiders were press). Histological data (VANACKER, unpubl.) confirm from the first generation of spiders coming from the same that gibbosus males secrete a nuptial gift in their groove; domain. The O. agrestis spiders were caught in Het the hunch of gibbosus is filled with gland cells with dif- Krawaalbos at Asse. The E. atra spiders were collected in ferent kinds of secretions. the nature reserve De Westhoek at De Panne. Here we describe intraspecific courtship behaviour in To keep the collected spiders alive as well as to breed the different Oedothorax species. Because only O. apica- them, the spiders were put into separate plastic cups tus males have a clearly distinct protuberance on the cara- (diameter : 4 cm and height : 2.5 cm), with a bottom of pace comparable with the hunch of gibbosus males, we plaster and a piece of moss. Young were fed assume that the possibility of the occurrence of a gustato- every two days with four (Isotoma spec. rial courtship is higher in O. apicatus than in O. fuscus, O. among others). After the second moult the spiders retusus and O. apicatus. received each time three fruit flies. At the same time three We also describe copulation behaviour of the different drops of water were added to maintain a relative humidity Oedothorax species. The copulation of near 100%. The spiders were kept in a climatic chamber (Blackwall, 1833) is also taken into account, because E. at a temperature of circa 20˚C and a photoperiod L :D of atra is closely related to the Oedothorax species accord- 16 :8. We opted for 20˚C because this is the best tempera- ing to the phylogenetic trees of HORMIGA (2000). E. atra ture to rear this dwarf spider species (ALDERWEIRELDT & is, like O. fuscus, O. retusus and O. apicatus, a very com- DE KEER, 1988; VANACKER et al., 2001a). mon species of open habitats. It can be supposed to be Copulations were observed with a WILD-binocular very active to increase its chances of survival in the open dissecting microscope and a cold light source. Each cou- field by evading natural predators. This active behaviour ple was observed for at least one hour and, in case of cop- can have consequences for the duration of copulation. O. ulation until at least half an hour after the copulation. To gibbosus and O. agrestis on the other hand are rare spe- take pictures of the courtship and copulation of Oedotho- cies, which are restricted to a very specific habitat. Such rax gibbosus during our observations, we used a digital species probably have the opportunity to copulate more camera (Nikon). slowly and for longer. We observed 81 copulations of O. gibbosus, 16 of O. Here, we investigate the hypothesis about the occur- fuscus, 22 of O. retusus, 24 of O. apicatus, 19 of O. rence of gustatorial courtship as well as the hypothesis agrestis and 12 of E. atra. Table 1 gives a complete sur- about copulation duration. Also the function of the web vey of the total number of gustatorial courtships and cop- during courtship and copulation is described. The litera- ulations that were observed for each species.

TABLE 1 The observed numbers of courtships and copulations in five Oedothorax species and Erigone atra.

Couples Couples Gustatorial Incomplete Complete Studied Couples with Species without with multiple courtship copulation copulation couples 1 copulation copulations mating

O. gibbosus gibbosus male 41 23 16 28 18 4 6 tuberosus male not observed 23 19 98 37 59 2 both males 41 46 35 126 55 63 8 O. fuscus not observed 6 10 26 13 12 1 O. retusus not observed 4 18 24 13 7 4 O. apicatus 18 ‘mini- courtships’ 8 16 27 8 12 7 O. agrestis not observed 6 13 13 9 0 4 E. atra not observed not observed 12 32 0 20 12

RESULTS which contains two phases. During the first phase the male approaches the female, both of the partners pump Oedothorax gibbosus (Blackwall, 1841) with the abdomen, the male cleans its palps or does up- The reproductive behaviour of O. gibbosus is first of all and down movements with the forelegs, and some males characterised by a pronounced courtship behaviour, make a specific dance to seduce the female. Such a dance Courtship and copulation in Oedothorax species 31

consists of movements in ‘8’ or ‘0’ forms, which they execute while approaching the female. During the second phase, physical contact is made between both partners. In the gibbosus morph the second phase is characterised by a gustatorial courtship (HEINE- MANN, 1998) (Table 3). The female brings her into the hairy groove and takes up the secretions (Fig. 1). Such a gustatorial courtship continues on average 9.53 ± 8.68 min (n=19) (Table 2). During the second phase of the courtship, the couple gets into copulation position and the male tries to insert a palp. Courtship behaviour of the tuberosus morph was also observed. Because this morph does not possess a groove that is filled with a secretion, this courtship is not gustatorial. Tuberosus can thus only perform the aforementioned courtship acts of the first phase. Most of the observed couples courted, but in some cases, they immediately started to copulate. Mostly the copulation itself took place upside down in the web in such a manner that the male was above the female (Fig. 2). The web has an important function in reproduction of this dwarf spider not only during gustato- rial courtship, but also during normal courtship and copula- tion, and probably also for the distribution of contact phe- romones. When copulation starts, the female chelicerae mostly stop making contact with the groove of her partner. Sometimes the transition from courtship into copulation Fig. 1. – Gustatorial courtship of Oedothorax gibbosus proceeds fluently; sometimes there are interruptions. In (female left, gibbosus male right). Note that the picture is turned 180˚ to be more clear; the normal courtship pos- some cases the male is dragged by the female, while its ture is male as well as female upside down, male above palp is still inserted. Other positions are also possible : on female. the bottom of the cup, on the moss or against the wall.

Fig. 2. – Copulation of Oedothorax gibbosus (gibbosus male right, female left). The haematodoch-bladder is also visible in the picture; the normal courtship posture is male as well as female upside-down, male above female.

During an insertion, sperm is pumped into the epigyne occur in this spider species; we observed 46 incomplete by means of swelling and shrinking of the haematodoch, and 35 complete copulations (Table 1). a bladder that is part of the male palp. Insertion of the palps occurs successively; a copulation with both palps is In O. gibbosus, one insertion takes on average about called a ‘complete copulation’, while if only one insertion 34.05 ± 1.68 min and the second insertion about 33.39 ± takes place we refer to an ‘incomplete copulation’ (HEINE- 0.09 min (Table 2). In eight studied couples ‘multiple MANN, 1998). Complete as well as incomplete copulations mating’ was noticed. 32 Liesbeth Maes, Danny Vanacker, Sylvia Pardo and Jean-Pierre Maelfait

TABLE 2 Duration of courtship and copulation of Oedothorax species.

Duration of courtship Duration of copulation

Oedothorax gibbosus 9.53 ± 8.68 min (n=19) (gustatorial courtship) 1st palp : –x = 34.05 ± 1.68 min, n= 81; 2nd palp : –x = 33.39 ± 0.09 min, n= 35

Oedothorax fuscus not observed 1st palp : –x = 4.09 ± 1.78 min, n= 16; 2nd palp : –x = 6.60 ± 0.96 min, n= 10

Oedothorax retusus a few seconds 1st palp : –x = 4.09 ± 0.97 min, n= 22; 2nd palp : –x =2.61 ± 0.61 min, n=18

Oedothorax apicatus a few seconds (‘mini-courtships’) 1st palp : –x = 5.67 ± 1.74 min, n= 24; 2nd palp : –x = 7.63 ± 1.41 min, n= 16

Oedothorax agrestis not observed 1st palp : –x= 6.95 ± 1.81 min, n= 19; 2nd palp : –x = 4.31 ± 0.75 min, n= 13

Oedothorax fuscus (Blackwall, 1834) copulation. O. fuscus spiders are usually much more active than O. gibbosus spiders. This could possibly Besides trilling of the forelegs, O. fuscus performed no form of courtship behaviour in the 17 studied couples explain the fact that there is no courtship and that the cop- (Table 3). Copulation in this species is not preceded by a ulation is much shorter. Another difference between the gustatorial courtship, or if it takes place it is very short. species is that O. gibbosus uses its head structures only We observed 16 copulations (Table 1). during the courtship and not while copulating, whereas Copulation position is comparable with that of O. gib- the O. fuscus female is in contact with the male cephalic bosus, but copulation duration is remarkably shorter (First structures during copulation. The head structures of O. palp : 5.88 ± 1.78 min, n=16; Second palp : 6.60 ± 0.96 fuscus are only used to force the spider into a better posi- min, n=10) (Table 2). The web is also very important for tion. Multiple mating was noticed in one couple.

TABLE 3 Contact of the female chelicerae with the male head structures in the five Oedothorax species.

Species Contact Contact Type of courtship during courtship during copulation

Oedothorax gibbosus X / Pronounced courtship Gustatorial courtship (gibbosus morph) Oedothorax fuscus / X No pronounced courtship No gustatorial courtship observed Oedothorax retusus / in some cases Pronounced courtship No gustatorial courtship observed Oedothorax agrestis / in some cases Distinct courtship No gustatorial courtship observed Oedothorax apicatus X X (hunch) Mini-courtships No gustatorial courtship observed

Oedothorax retusus (Westring, 1851) bottom and another one against the wall of the cup. The position is comparable with that of O. gibbosus. Like O. In this species there is, in most cases, a courtship fuscus, copulation duration of O. retusus is much shorter (Table 3). The most common courtship acts are trembling than that of O. gibbosus (First palp : 4.09 ± 0.97 min, with the first pair of legs, plucking on the web with the n=22; Second palp : 2.61 ± 0.61 min, n=18) (Table 2). In forelegs, cleaning the palps, etc. In one case, the male four studied couples, multiple mating was noticed. In executed some kind of dance; by sinking a few times most cases, the female mouthparts were situated above through its legs, alternating with raising itself, it worked the head structures of the male during copulation. itself up and down. This behaviour took place while it stood erect in the web, and was combined with trembling Oedothorax agrestis (BLACKWALL, 1851) of the opisthosome. In the second phase of the courtship, both partners touched each other with the forelegs and put In O. agrestis no obvious courtship behaviour was themselves into copulation position. Meanwhile the male noticed (Table 3). The copulation position was compara- attempted to insert a palp. ble with that of O. gibbosus. Although this species behaves rather calmly, the copulation duration was The copulation itself usually takes place upside down remarkably shorter than that of O. gibbosus (First palp : under the web, although one copulation took place on the 6.95 ± 1.81 min, n=19; Second palp : 4.31 ± 0.75 min, Courtship and copulation in Oedothorax species 33

n=13) (Table 2). One couple copulated twice. These DISCUSSION results are in a way different from those formulated by SCHLEGELMILCH (1974) who mentioned an average dura- The majority of the erigonine males carry head struc- tion of insertion of 7.5 min. tures of various kinds : elevations, accretions, notches, grooves and hair fields. SCHAIBLE & GACK (1987) men- According to SCHAIBLE et al. (1986), there is no contact tioned that all species possessing such structures, have in between the female chelicerae and the male head struc- common that the chelicerae of the female makes contact tures. In one case we observed, however, that the female with the male head structures during copulation. This mouthparts were situated above the male head structures. statement appears not to be true; with E. atra, for exam- In the other cases there was no contact during the copula- ple, there was no contact observed, neither during court- tion. In four studied couples, multiple mating was ship, nor during copulation (SCHAIBLE et al., 1986). noticed. SCHAIBLE et al. (1986) did not observe any contact of the female mouthparts with the male head structures. Our Oedothorax apicatus (Blackwall, 1850) observations, however, showed one case in which the female chelicerae were above the head structures of the This representative of the Oedothorax genus is remark- male. able for its short, nervous and fierce copulation (First ± ± Although many dwarf spiders court before copulating, palp : 5.67 1.74 min, n=24; Second palp : 7.63 1.41 we found mention in the literature of few dwarf spider min, n=16) (Table 2). In many cases the female held the species that make physical contact during courtship : protuberance (hunch) of the male between the chelicerae Baryphyma pratense (Blackwall, 1861) and (seven observations). Both partners trilled a lot while cop- brevipes (Westring, 1851) (SCHLEGELMILCH, 1974; SCHAI- ulating and the female usually dragged the male violently BLE et al., 1986). Other spider species which make cheli- and over long distances. ceral contact during courtship are Atypus muralis The presence of the hunch as well as the solid stitch Bertkau, 1890 and Atypus piceus (Sulzer, 1776) (Atypi- between the palp and the epigyne, assures that the copula- dae), Avicularia avicularia (Linnaeus, 1758), Grammos- tion is not interrupted. The copulation position is strongly tola mollicoma (Ausserer, 1875) and Phormictopus can- comparable with that of O. gibbosus, with exception of ceridis (Latreille, 1806) (Therophosidae), Scytodes the continuing contact between hunch and chelicerae. thoracica (Latreille, 1802) and Scytodes velutina Because of the nervous copulation, the function of the Heineken & Lowe, 1832 (Scytodidae), Holocnemus web is apparently of less importance for copulation in O. pluchei (Scopoli, 1763), Pholcus phalangioides (Fuesslin, apicatus. 1775) (Pholcidae), Segestria bavarica C. L. Koch, 1843, Segestria florentina (Rossi, 1790) and Segestria senocu- Analogously with the courtship of other more active latata (Linnaeus, 1758) (Segestriidae), Pachygnatha cler- spiders, such as O. fuscus and O. retusus, the courtship of cki Sundevall, 1823, Pachygnatha degeeri (Sundevall, O. apicatus is very short and nervous. Moreover, several 1830) and Pachygnatha listeri (Sundevall, 1830), Tetrag- times so-called “mini-courtships” were executed; the natha extensa (Linnaeus, 1758), Tetragnatha montana female held the male hunch by means of her chelicerae, in Simon, 1874 and Tetragnatha nigrita (Lendl, 1886) addition to which the female touched the head of the male (Tetragnathidae), Nigma walckenaeri (Roewer, 1951) with the first pair of legs (Table 3). During this “mini- (Dictynidae), Clubiona germanica (Thorell, 1871) and courtship”, however, the female did not make sucking or Clubiona terrestris (Westring, 1851) (Clubionidae) biting movements with the mouth, as was the case in O. (HUBER, 1998). gibbosus. In seven studied couples ‘multiple mating’ was The copulation duration of Oedothorax gibbosus is noticed. comparable with that of Ceratinella brevipes (Westring, 1851), Diplocephalus latifrons (O.P.-Cambridge, 1863), Erigone atra (Blackwall, 1833) Gonatium rubellum (Blackwall, 1841) (SCHLEGELMILCH, 1974; SCHAIBLE et al., 1986). In other spider families, for An elaborate courtship was not observed in E. atra. example Dysdera erythrina (Walckenaer, 1802) (Dysderi- While approaching the female, the male moved its palps dae), Oonop placidus Dalmas, 1916 (Oonopidae), Pis- up and down, trembled briefly with its forelegs and aura mirabilis (Clerck, 1757) (Pisauridae), Xysticus pumped a single time with its abdomen. cristatus (Clerck, 1757) (Thomisidae) and Heliophanus cypreus (Walckenaer, 1802) (Salticidae) have similar cop- The copulation is different from that of the Oedothorax ulation duration to Oedothorax gibbosus (HUBER, 1998). species : instead of two continuous insertions we observed, in this case here, series of very short insertions Our results show that, within the genus Oedothorax, O. (9.81 ± 5.32 min, n=93), which could be linked to one gibbosus differs from its sister species by executing a another to form longer periods. During such a series, the longer courtship, certainly in the case of the gibbosus male inserts one , pumps once (haematodoch male, as well as a longer copulation. We observed gusta- swells and shrinks one time), removes the palp, cleans it, torial courtship only in O. gibbosus, although we also inserts the other (in some cases the same) palp, etc. The observed “mini-courtships” in O. apicatus. aforementioned longer periods continued for about 83.42 The gibbosus morph has a hairy groove in which a nup- ± 5.99 min (n=12) and embraced, in four couples seven, tial gift and/or pheromones are secreted (VANACKER et al., in one couple eight, in six couples nine and in the other in press). The tuberosus morph, on the contrary, has no couple eleven series of insertions. distinct head structures. They have few cephalic gland 34 Liesbeth Maes, Danny Vanacker, Sylvia Pardo and Jean-Pierre Maelfait

cells (VANACKER, unpublished results) and probably this The copulation of many species in which the male pos- is also the case in the males of Oedothorax species with- sesses head structures, is characterised by an anchorage of out distinct cephalic structures. O. apicatus can be the male head structures by the female chelicerae regarded as taking an intermediate position : an O. apica- (Hypomma bituberculatum (Wider, 1834), Walckenaeria tus male is characterised by one narrow hunch on its corniculans (O.P.-Cambridge, 1875) : SCHLEGELMILCH, cephalothorax. The possible occurrence of a few gland 1974). O. gibbosus only shows physical contact of the cells could explain the appearance of the “mini-court- female chelicerae with the groove and hunch of the gib- ships” in this species. The results of MEIJER (1976) indi- bosus male, during gustatorial courtship. SCHAIBLE & rectly confirm this hypothesis; the author found remnants GACK (1987) suggested that the function of the male head of secretions on spiders that were caught in pitfalls, structures is to fix the copulation posture. This is probably including on O. apicatus. This article also mentions pos- not the most common function, because there is, for sible secretions in Troxochrus scabriculus (Westring, example, in most cases no retained contact between the 1851), which is also known for its male dimorphism. Fur- chelicerae and the male head structures during copulation ther histological and TEM research will study the occur- of O. gibbosus. rence of such cells. Oedothorax species have a relatively short copulation duration, excepted for O. gibbosus, where average copu- Probably most erigonine males possess gland cells lation duration is strikingly longer than that of the other (some species more than others). The gustatorial court- Oedothorax species. The longest copulation duration ship is most pronounced in O. gibbosus (probably linked belongs to Erigone atra (50’-75’/ insertion) – but this last to the male dimorphism of this species), but the mini- species has another copulation technique – and the short- courtships of O. apicatus also have in most cases a ‘gus- est to Tmeticus graminicolus (5’ per insertion). The tatorial’ character (MEIJER, 1976). It is possible that the extremely high copulation duration of O. gibbosus is very biting movements only appear in O. gibbosus, because remarkable. Why, however, is such a long copulation nec- the substance, in that species, is secreted in a groove. In essary, if closely related species can achieve sperm trans- this way, heavier sucking movements are necessary for fer in a much shorter time? A longer copulation time the female to reach the secretion. Another possibility is leads to a higher risk of being caught by a predator. Possi- that because of this groove, the female first places some bly this risk is more pronounced for species living in open saliva into the groove and then sucks up (SCHAIBLE & habitats than in more rare ones. There is for example no GACK, 1987). We have observed this several times specific natural predator of O. gibbosus in the studied (VANACKER, unpubl.). Because the possible secretions in population in the public nature reserve Het Walenbos; the the other Oedothorax species are superficial (i.e. not in a lycosid spider Pirata hygrophilus Thorell, 1872 occurs at groove), females of this species do not have to execute high density but does not predate on O. gibbosus pronounced bite and suck movements. Courtship of the (VANACKER, unpubl.). That the copulation of the rare O. kind seen in O. apicatus or simple contact during copula- agrestis is short is in disagreement with the above-men- tion as in O. retusus and O. agrestis could also have a tioned hypothesis. However, this species behaves rather gustatorial character. Gustatorial contact in these last spe- calmly, which is comparable to the activity of the also cies is not so obvious, because the contact is much shorter rare O. gibbosus. and the secretions are probably less. In O. fuscus, this contact is probably so short that it almost cannot be Multiple mating occurs very frequently in Oedothorax observed during copulation. It is also possible that there and Erigone. The number of couples that performed mul- are secretions in E. atra. Superficial contacts between tiple mating in O. gibbosus was not very high in the female mouthparts and male head structures to exchange described experiment, but in other experiments with secretions remain a possibility. longer observation periods multiple mating was also very frequent in both male morphs of O. gibbosus (VANACKER, If we compare courtship and copulation behaviour of unpubl.). The web has an important function in the repro- Oedothorax species with the other dwarf spiders, we can duction of Oedothorax spiders. It seems reasonable to conclude that the courtship behaviour is comparable assume the importance of the web in reproduction within the subfamily Erigoninae. Oedothorax species are decreases with the activity of the spiders. characterized by a copulation of two insertions, which is The longer courtship and copulation time could also be typical for most dwarf spiders. This also appears in some a consequence of the occurrence of male dimorphism in other dwarf spider species, but there are also species this species caused by male competition and sperm com- whose copulations contain several series of insertions, petition. More ethological and genetic research, such as such as Erigone species, Tmeticus graminicolus, etc. We construction of a phylogenetic tree of Oedothorax on the observed in E. atra series of very short insertions, which basis of DNA, is necessary to give a decisive answer can be linked to each other to form longer periods. SCH- about this. LEGELMILCH (1974) also mentioned this, but he claims an increasing duration of insertion; we found on the contrary ACKNOWLEDGEMENTS more or less regular insertion times. The copulation dura- tion, according to SCHLEGELMILCH (1974) is 100-150 We are grateful to Domir De Bakker, Frederik Hendrickx and minutes; in our results we found an average duration of ± Dries Bonte for checking the identification of the living spiders. 83.5 7.78 min (n=12) per longer period. Erigone den- For catching the animals we could depend on Katrijn Deroose, tipalpis (Wider, 1843) and Erigone longipalpis (Sun- Viki Vandomme, Lut Van Nieuwenhuyse, Domir De Bakker and devall, 1830) seem to have similar copulation behaviour Léon Baert. Danny Vanacker has a PhD grant from the Founda- to that of E. atra (SCHLEGELMILCH, 1978). tion for Scientific Research – Flanders. Courtship and copulation in Oedothorax species 35

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